Just this last Sunday, Vurve made the decision to switch our primary code hosting from an internal SVN repository to Github. The process was surprisingly easy, and for most repositories this proved to be as simple as setting up a comprehensive svnauthors file, checking your projects out of svn with git-svn, adding a new remote (in this case, Github itself), and pushing your repository again. The process we followed for the migration is detailed on Github's wiki here.
One of the many reasons why we wanted to move to Github was also to share some of the code projects we've been working on internally, and to be involved in the development of the technology that powers our services. Keep an eye on our Github page!
Mike, Open Source Anarchist